GB638492A - Improvements in and relating to the revivification of bone char - Google Patents

Abstract

<PICT:0638492/III/1> A batch or continuous process for the revivification of particulate bone char comprises heating it, preferably at 450-550 DEG C., while maintained in a fluidized state, but not as an p "entrained stream," by a counter or cocurrent stream of an inert gas, e.g. nitrogen, superheated steam, or a mixture thereof, or the gaseous products of combustion of solid, liquid, or gaseous fuels. The bone char may be heated either directly or indirectly, or both. A sufficient amount, say 2 per cent by volume of free oxygen may be present to remove some of the carbonaceous material in the char. The char may be predried to 8-10 per cent by weight moisture. Wet spent bone char to be revivified passes from hopper 14 to drier 15, having conical bottom 19, where it contacts warm gases from pipe 16, and passes thence to annular space 21, having inner shell 24 with louvres 25, lagged outer shell 23, and central combustion chamber 26, where drying is completed. The char then flows to larger annular space 34, wherein it is maintained in the fluid state by hot gases escaping through channels 30 from refractory lined combustion chamber 26, which is supplied with combustible gas and air at 32 and may have refractory thermal accumulator 29 and external fins to assist heat distribution. The hot char passes down ducts 35, cooled by air drawn through sleeves 36, to hopper 39. The air from sleeves 36 is admixed with hot gases withdrawn through louvres 25 and from the top of space 34 and fed through pipe 16 as drying gas. The apparatus may have more than one combustion chamber, or there may be a single annular space of uniform cross-section surrounding the combustion chamber. A simpler apparatus is also described in the Provisional Specification. Specification 569,691 is referred to.